(1) Field of the Invention
The present invention pertains to a bearing race for a bearing and a mount or support for the bearing. More specifically, the invention pertains to an improved design for a bearing race which maintains its annular bearing surface when it is mounted to a mount and the mount is subjected to a load which causes distortion of the mount. The manner in which the race is connected to the mount prevents the distortion of the mount from being transferred from the mount to the race when the mount is loaded and distorted.
(2) Description of the Related Art
Roller bearings are known in the art and provide an effective means for controlling rotary motion of one object relative to another. Bearings of this type are effective in controlling rotary motion about an axis of rotation. Typically, the roller bearing comprises an outer race and an inner race with a plurality of rollers positioned between the races in rolling contact with the races. Generally, a cage is used to maintain the rollers in a fixed orientation between the races and in rolling contact with the races. In a typical installation of the roller bearing, one of the races is mounted to a journal of a rotating object, for instance, a spindle, and the other of the races is mounted to a fixed object, such as a housing for the spindle. In this way, the rotary motion of the one object may be transferred to the race such that the race and the rotating object rotate through the action of the rollers in a controlled manner relative to the other of the races and the stationary object.
As the rollers of the bearing and the surfaces upon which they roll are critical to ensuring proper operation of the bearing, it is essential that the bearing surfaces and the rollers have tightly controlled dimensions and shapes, including diameter size, roundness, cylindricity, etc. Additionally, it is critical that there be minimal circular run out between the races. Over time, even small imperfections and deviations in the rollers and the bearing surfaces can cause excessive and accelerated wear of the bearing leading to premature failure of the bearing.
Conventional bearings are well suited for applications where there is rotary motion between a shaft and a stationary object. Typically, the races are fixedly attached to their mounts or supports and the mounts are not subjected to external loads which would cause excessive distortion of the mount or support. In applications where there are excessive forces, typically the size of the bearing is increased to compensate for the force and to provide a more rigid connection. However, in applications where size must be constrained and the mounts are subjected to external loads which cause the mounts to distort, a larger bearing cannot be used and the distortion of the mount transfers directly to the race thereby deforming the bearing surface and causing the bearing to fail prematurely.
In the application giving rise to the invention disclosed herein, the roller bearing is an inboard pitch bearing provided in the rotor hub of a helicopter. In this application, the roller bearing provides a rotational hinge about which the helicopter blade pitch is changed. The rotor hub assembly is subjected to an extreme amount of centrifugal force developed from the rotor blades as they rotate to generate lift for the helicopter, and as the rotor hub retains the blades in place under the centrifugal force in which the blades operate, there is distortion of the blade supporting members, including the mounts and supports for the inboard pitch bearing. Designs which have used a conventional roller bearing in this application have had problems because the high centrifugal forces developed by the rotor blades distort the inboard pitch bearing mounts causing deformation of the inboard pitch bearing race and premature failure of the inboard pitch bearing.
Thus, what is needed is a bearing race which is capable of transferring a bearing transfer load to its mount or receiving the bearing transfer load from its mount while the bearing surface or the race maintains its annular shape independently of an external load applied to the mount which distorts the mount. Such a bearing race and mount would be of relatively simple construction and have relatively few parts so that manufacturing, inventory and installation costs associated with the bearing and the mount could be kept to a minimum. Such a race and mount would be part of a compact and lightweight assembly, thereby meeting the stringent space and weight limitations and other constraints dictated by the application.